Re: [PATCH v5 00/15] block: fix the zone write granularity and the zone append limit

[Niklas Cassel <cassel@kernel.org>]

On Fri, Sep 18, 2026 at 07:29:08PM +0200, Niklas Cassel wrote:
> Hello Stefan, Kevin, and everyone else,
> 
> This series fixes how QEMU reports and enforces the two constraints that a
> zoned device places on a write to a sequential zone: the write granularity,
> and the largest zone append that it accepts. It also fixes two bugs in the
> zone append emulation in file-posix, one of which a guest can reach.
> 
> Most of it is preparation for Sam Li's zoned qcow2 series. The first two
> patches are taken directly from there, as they are unrelated to qcow2.
> 
> Neither of the two values that this series touches is derived from
> BlockLimits any more, which was Stefan's objection to v4: the guest has
> been told the value, so it is part of the migration stream, and a
> destination host whose disks report something else breaks the guest. The
> write granularity now comes from the logical and the physical block size,
> the append limit from a property, and a backend that needs more than the
> configuration can express is refused at realize. The conditions that hold
> for every backend rather than for a particular one moved into the block
> layer, where they also cover callers that are not a device model.
> 
> Changes since v4:
> - Patch 4 is new: a helper to check if a zone is conventional. The device
>   model tested that by reaching into bs->wps->wp[] and decoding the bit
>   that the block layer encodes it in, which two patches here would have
>   added two more instances of.
> - Patch 5: derive the granularity from the logical and the physical block
>   size rather than from BlockLimits. Document
>   BlockLimits.write_granularity. Dropped Damien's Reviewed-by, as the
>   derivation itself changed.
> - Patch 7: also refuse a backend that needs a coarser granularity than the
>   block sizes can express. Dropped Damien's Reviewed-by, as the patch
>   gained a check.
> - Patch 9 is new: reject an append larger than a zone. This is the bound
>   that the device model gives up by no longer deriving its own limit.
> - Patch 11: a max-append-sectors property rather than a value derived from
>   the backend. It now precedes patch 12, which v4 had first; that way round
>   left a commit that reported a zero limit to the guest.
> - Patch 12: remove BlockLimits.max_append_sectors, rather than have
>   file-posix report max_hw_transfer for it. Nothing reads the field once
>   virtio-blk takes its limit from a property, and file-posix was its only
>   writer. Damien, your Reviewed-by was for reporting max_hw_transfer, so I
>   have dropped it.
> - Patch 15 is new: the CoroutineIOCompletion cleanup.

Stefan, it seems like my tooling failed to pick up your tags because they
were multipart messages.... I'm very sorry about that.

Patches that you have reviewed, and are supposed to have your R-b tag:
1, 2, 3, 6, 8, 10, 13, 14



Patches that you need to review - changed so much that I dropped tags:
7, 12

Patches that you need to review - patches that you had comments on:
5, 11

Patches that you need to review - patches that are new:
4, 9, 15



Kind regards,
Niklas